The present invention relates to a flat panel display device having electron beam guides and particularly to such a display device in which the beam guides include means for modulating the electron beams.
U.S. Pat. No. 4,031,427 to T. O. Stanley, issued June 21, 1977, entitled "Flat Cathode Ray Tube" describes a flat, cathodoluminescent display device which includes in an evacuated envelope beam guides extending along the back wall of the envelope from a gun structure which generates electrons and directs the electrons as beams into the beam guides. The beam guides confine the electrons in the beams as the beams travel along paths parallel to the front wall of the envelope and selectively deflect the beams toward a phosphor screen on the front wall at selected points along the paths of the beams.
U.S. Pat. No. 4,088,920 to W. W. Siekanowicz et al., issued May 9, 1978, entitled "Flat Display Device with Beam Guide" describes a beam guide for use in the display device of the type described in U.S. Pat. No. 4,031,427. The beam guide includes a pair of spaced, parallel plates extending along and spaced from the back wall of the envelope. The plates have a plurality of aligned openings therethrough with the openings being arranged in rows extending longitudinally along the paths of the beams. Each longitudinal row of the openings constitutes a separate beam guide.
Copending applicatons for U.S. patent, Ser. No. 784,365 of R. A. Gange, filed Apr. 4, 1977, entitled "Cathode Structure and Method of Operating the Same" and Ser. No. 835,772 of C. H. Anderson, filed Sept. 22, 1977, entitled "Beam Guide for Display Device with Beam Injection Means", disclose gun structures for use in the display device of the type described in U.S. Pat. No. 4,031,427. The gun structures include a line cathode having modulation or control electrodes spaced along the line cathode. Potentials applied to the modulation electrodes cause the electrons generated by the cathode to be emitted therefrom in the form of beams. The gun structures may include isolation electrodes between the modulation electrodes to assist in confining the electrons in the beams emitted from the gun structure and guiding the beams into the guide structure.
In the gun structure of the Anderson application, Ser. No. 835,772, the modulation electrodes must be accurately dimensioned and positioned with respect to the electron guides. If the edges of the two overlapping modulation electrodes which face the guides do not have a similar contour and are not equidistant from the guide, the beam will be pulled off center and will not enter the guide properly. Therefore, during the fabrication of the display device, the modulation electrodes must be positioned with a high degree of tolerance.